Saelens N A, De Smit A A
Department of Orthodontics, Free University of Brussels, Belgium.
Eur J Orthod. 1998 Jun;20(3):225-36. doi: 10.1093/ejo/20.3.225.
Pre- and post-treatment lateral cephalograms of two extraction groups (E4: extraction of the four first premolars; E5: extraction of the four second premolars) and one non-extraction group (NE) were evaluated in patients treated with Begg appliances. It was the intention to investigate the initial amount of crowding, the changes in the position of incisors and molars, the soft tissue profile changes, and the clinical outcome. Ten linear and eight angular measurements were analysed. In order to assess the initial amount of crowding, the Arch Length Discrepancy (ALD) was measured on dental casts taken before treatment. The clinical outcome was evaluated using the PAR Index. The mean pretreatment crowding was nearly twice as large in group E4 when compared with groups E5 and NE. This difference was the main reason for the higher mean PAR score (21.4) for E4 when compared with E5 (15.4) and NE (15.2). In addition, for the cephalometric pretreatment values, some significant differences between the three groups were found: the upper and lower incisors and the lower lip region relative to the pterygomaxillary vertical plane (PMV) were more protrusive in group E5; the inter-incisal angle in both extraction groups was smaller than in the non-extraction group. During treatment, the lower incisor position relative to PMV did not change significantly, and the upper incisors moved backward approximately 2 mm in both extraction groups. This was not reflected in a significant change in lip position. In the non-extraction group, tooth alignment was accompanied by a significant proclination of the incisors, and a comparable forward movement in the lip region when measured in relation to PMV. In the three types of cases, no unfavourable changes in the facial profile were seen. A mean enlargement of about 6 degrees normalized the inter-incisal angle in both extraction groups, while in the non-extraction group the inter-incisal angle became smaller than the norm value. In the three types of cases, upper and lower molars were moved mesially. This movement was higher in group E5 than E4, and lower in the NE cases. Mainly due to the case selection (Class I or very mild Class II or Class III malocclusions), the pretreatment PAR Index was not very high. The percentage reduction for the three groups was higher than 90 per cent. With post-treatment mean PAR scores less than 2, groups E4, E5, and NE can be regarded as having an almost ideal clinical outcome.
对使用Begg矫治器治疗的两个拔牙组（E4：拔除四颗第一前磨牙；E5：拔除四颗第二前磨牙）和一个非拔牙组（NE）治疗前和治疗后的头颅侧位片进行了评估。目的是研究初始拥挤量、切牙和磨牙位置的变化、软组织侧貌变化以及临床结果。分析了10项线性测量和8项角度测量。为了评估初始拥挤量，在治疗前取的石膏模型上测量牙弓长度差异（ALD）。使用PAR指数评估临床结果。与E5组和NE组相比，E4组的平均治疗前拥挤程度几乎高出一倍。这一差异是E4组平均PAR评分（21.4）高于E5组（15.4）和NE组（15.2）的主要原因。此外，对于头颅测量的治疗前值，三组之间发现了一些显著差异：相对于翼上颌垂直平面（PMV），E5组的上下切牙和下唇区域更突出；两个拔牙组的切牙间角均小于非拔牙组。治疗期间，相对于PMV，下切牙位置无显著变化，两个拔牙组的上切牙均向后移动约2mm。这并未反映在唇部位置的显著变化上。在非拔牙组中，牙齿排齐伴随着切牙的显著前倾，以及相对于PMV测量时唇部区域类似的向前移动。在三种类型的病例中，面部侧貌均未出现不利变化。两个拔牙组的切牙间角平均增大约6度后恢复正常，而非拔牙组的切牙间角变得小于正常值。在三种类型的病例中，上下磨牙均向近中移动。E5组的这种移动高于E4组，NE组病例中的移动较低。主要由于病例选择（I类或非常轻度的II类或III类错牙合），治疗前PAR指数不是很高。三组的降低百分比均高于90%。治疗后平均PAR评分小于2，E4组、E5组和NE组可被视为具有几乎理想的临床结果。
